Should the US Adopt Metric Standards?

Seven years ago, Robert Lipsett, engineering manager at Danaher Motion, wrote a Design News blog about the dwindling reasons for the US to remain wedded to nonmetric standards. Surprisingly, this blog post received no comments for or against. But the need remains for the US to finally jump to the metric system, and I bet it wouldn't take as long for us to adopt metric units as some skeptics think.

Canada, our largest trading partner, adopted metric standards in the 1970s, although commercial relations with the US still require the use of some English units for many products that cross the border. I have traveled to Canada many times, and I found it easy to adapt to the use of grams for product weights, liters for gasoline purchases, and kilometers for distance. Kilopascals for pressure take a longer adjustment, but how often do we think about barometric weather readings? Perhaps the use of metric units in college and grad school makes them more familiar to us engineers and scientists.

The US exports products worldwide, so many manufacturers already use metric fasteners and measurements. Semiconductor suppliers provide device-package specifications in metric and English units, and even kitchen measuring cups and measuring spoons come marked with metric and English units. And consumer products include metric and English units. So a complete switch to metric units wouldn't require much effort -- just a bit more attention to measurements we already see.

Metrication wouldn't immediately cause a wholesale switch to millimeters and meters from feet and inches. In Canada, for example, I can still buy an eight-foot 2 x 4 and a six-inch-wide piece of siding. Here in the US, we could still buy screws sized as 6-32 or 10-24, though more products would use metric threads and sizes. Many of the machine tools I use already have metric designations, and I have a helpful conversion chart for those that don't.

US residents already use mixed units such as x milligrams of caffeine per ounce of cola drink and y grams of fat per serving of, say, cookies. The standard method for sizing tires combines millimeters (for tread width) with inches (for rim diameter). Tire inflation for a typical passenger car is 30psi, which is also given in its metric equivalent (207kPa, or kilopascals). Light bulbs use eighths of an inch for bulb diameter and full inches for fluorescent tube lengths, but the socket is always measured in millimeters.

So metrication creeps forward in the US, but it's time to make the last 100-meter run and, to borrow Nike's slogan, just do it.

Do you agree with Jon? Tell us your opinion in the comments section below.

Jon, I agree about the ability to use Phillips and slot head screwdrivers on everything. Those are probably the two tools I use most around the house. I've encountered Robertson screws occasionally, but find it harder to turn them (even using the correct tool!) since the geometry takes more torque.

I believe the USA already has. I have found using both metric and imperial measurements can be helpful for different applications. Sometimes using one or the other give the perfect fit. For example, no imperial/english standard size is close to 0.700", but the metric 18mm is almost perfect. So, I would go with the standard 18mm for parts, sizes, etc.

I like the fact that the USA has both in practice. It give us the ability to choose.

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